Magneto



Dec. 15, 1942. c, WALL 2,304,866

MAGNETO Filed Dec so, 1939 Fig.2.

lnvenbo'r' I Alexander C. WaH, 9 )vnn a. JM M is Attorney may in turn berotated by the camshaft or by the crankshaft through suitable PatentedDec. 15, 1942 MAGNETO Alexander C. Wall, Schenectady, N. Y., assignor toGeneral Electric Company,

New York a corporation of Application December 30, 1939, Serial No.311,797

4 Claims. (Cl. 171-209) My invention relates to an electric ignitionsystem for internal combustion engines. and more particularly tomagnetos of the inductor type.

Heretofore magnetos of the above mentioned type have been operated withpermanent magnets and generating coils on the stationary member thereofand with a rotatable member so arranged as to produce the build up offlux first in one and then in the opposite direction through generatingcoils. In magnetos of this type which have used this flux reversal inthe generating coils, the permanent magnet which is not producing theuseful flux at the particular moment is so ar ranged as to be shortcircuited by the rotatable member. In accordance with my invention,however, the idle permanent magnet is opencircuited.

Further objects and advantages of my invention will become apparent fromthe following description referring to the accompanying drawing, and thefeatures of novelty which characterize my invention will be pointed outwith particularity in the claims annexed to and forming a part of thisspecification.

Inthe drawing Fig. 1 diagrammatically illustrates a conventionalignition circuit provided with my improved magneto, and Fig. 2illustrates the magneto shown in Fig. 1.

- Referring to the drawing, in Fig. 1 I have illustrated an ignitionsystem for an internal combustion engine including a magneto ill with acoil member having a primary winding II and a secondary winding l2. Theprimary winding II has in circuit with it a conventional capacitor l3and a conventional breaker terrupts the primary breaker I4 is actuatedby winding circuit. This a cam member l5 which directly, gears. I haveshown two breakers which are operated by the same cam and they are soconstructed that the primary winding circuit is broken each time thecurrent in the primary winding reaches its maximum value. Of course,only one, or any number of breakers may be' used to effect this"operation. The secondary winding I2 is in cir-' cuit with aconventional distributor it. This distributor includes a rotatingelectrode and a series of stationary contacts each of which is connectedto a spark plug I1. Only one such connection is shown in Fig. 1

.As more completely shown in Fig; 2 my improved magneto includes a coremember l8 which is magnetically associated with the coil member. Thecore member also has a plurality of pole pieces I! which cooperate witha rotat- M which periodically in-- will assume able member 20.Magnetically connected with the core member I8 I also provide permanentfield magnets 2i which are relatively short and have high coerciveforce. Any suitable magnet material may be used, andiron-aluminum-nickel alloy described in U. S. Patent No. 1,947,274,Ruder, to be particularly eflicient. The permanent magnets may also haveon an end thereof pole faces 22 which also cooperate with the rotatablemember. The pole faces 22 and the pole pieces l8 are so constructed andarranged that they lie on the arc of a circle. The rotatable member 20has a plurality of teeth 23', the peripheral faces of which being ofslightly less width than the pole faces 22 so as to give a more rapidchange of flux and so as to maintain a higher voltage at lower speeds.In the illustrated embodiment of my invention nine such teeth areprovided. However, it is to be understood that any suitable number ofteeth may be provided on the rotatable member depending on the number ofcylinders in the internal combustion engine. The illustrated magneto,therefore, has application with an 18 cylinder internal combustionengine, since 18 sparks will be produced for every complete rotation ofthe rotatable member. This is effected by providing the distance betweensimilar portions of each of the polepieces substantially equal fone-half the tooth pitch of the rotatable member. The distance between apole piece and the adjacent per- Y manent magnet pole face issubstantially equal to the distance between the two pole pieces. Withthe rotatable member shown in the positionas shown in Fig. 2, flux willpass from the north pole of the right hand permanent magnet into theadjacent tooth on the rotor and then into the next tooth which liesopposite pole piece.

member and to the southpole of the permanent magnet. When the rotatablemember has moved a distance equal to one-half its tooth pitch, the rotorthe position shown in the dotted lines in Fig. 2, and flux will now passfrom the north The flux will then pass to the core pole of the left handpermanent magnet into jacent the rotatable member, but it is obvious Ihave found that the' the left hand 1 link the coil member and then passthe coil member in the opposite direction from that the south pole oieach magnet may be placed adjacent the rotatable member. It is onlynecessary that each magnet have like poles pointing toward and away iromthe rotatable member. It may be seen then that as the magnetic path oieach magnet is completed, the magnetic path oi the other magnet is opencircuited. In construcnet. It was thought necessary to short circuit a'magnet which is not in use. I have found, however, that it is notnecessary to short circuit the magnet which is not at the moment beingused to produce the ignition spark. In order to produce the shortcircuiting magnetic path in the magnetos heretofore used it wasnecessary to use large pole faces attached to the ends oi the magnets.With my improved magnet arrangement such large pole faces are dispensedwith, and in addition the iron necessary on the rotatable element toproduce this short circuiting is dispensed with. Therefore, if the shortcircuiting oi the idle magnet were caused by the same rotor tooth thatcarried the useful flux, it will be seen, that with my improvedarrangement, the flux which a single rotor tooth adjacent a pole piecemust carry is substantially reduced to one-half, thus allowing adecrease in irm oi the tooth to one-half. This results in a substantialsaving in weight and space which is desirable and particularly importantwhen the magneto is to be used on aircraft.

Modifications oi the particular arrangements which I have disclosedembodying my invention will occur to those skilled in the art, so that Ido not desire my invention to be limited to the particular arrangementsset forth and I intend in the appended claims to cover all modificationswhich do not depart from the spirit and scope oi my invention.

What I claim as new and desire to secure by Letters Patent oi the UnitedStates is:-

1. An ignition system for an internal combustion engine including amagneto having a coil member, a plurality oi permanent magnets, a

- core member, said magnets having ends connected to said core member toiorm magnetic paths between said coil member and said magpermanent oionly one oi said magnets nets, and means including a rotatable memberfor completing in succession the magnetic path of only one oi saidmagnets at a. time through said coil core member and said rotatablemember.

2. Anignition system for an internal combustion engine including amagneto having a coil member, a plurality oi permanent magnets, a coremember, said magnets having ends connected to said core member to iormmagnetic paths between said coil member and said magnets, a plurality oipole pieces magnetically associated with said core member, and meansincluding a rotatable member arranged to rotate for completing insuccession the magnetic path oi only one oi said magnets at a time bysaid rotatable member.

3. An ignition system ior an internal combustion engine including amagneto having a coil member; a plurality oi permanent magnets, a coremember, said magnets having ends connected to said core member to formmagnetic paths between said coil member and said masnets, a plurality ofpole pieces magnetically associated with said core member, and meansincluding a rotatable member arranged to rotate for completing insuccession the magnetic path at a time by said rotatable member, saidmagnets being so arranged that the completion oi one of said magneticpaths produces a flux in said core member opposite to the flux producedby the path immediately beiore completed.

4. A magneto including a rotatable inductor having a plurality oi teeth,a coil member, a plurality of permanent magnets having high coerciveforce, a core member threading said coil member, said magnets havingends of like polarity connected to said core member so as to iormmagnetic paths between said coil member and said magnets and ends oilike polarity arranged in the arc oi a circle so as to cooperate withsaid teeth oi said rotatable inductor, and a plurality of pole piecesextending from said core member and arranged in the arc oi a circle soas to cooperate with said teeth oi said rotatable inductor, one of saidmagnets and one oi said pole pieces extending from said core memberadjacent each 01! the opposite sides oi said coil member, meansincluding the arrangement oi said teeth on said rotatable memberrelative to said magnets and said pole pieces ior completing insuccession the mggnetic path of only one oi-said' magnets at a ALEXANDERC. WALL.

